Iroha • Origin: Mid-Edo period • Status: Only daughter of a courier shop owner (no surname) • Personality: Bright, energetic, and tomboyish. She speaks roughly but is full of curiosity. • Traits/Dreams: Has a strong interest in mathematics (Wasan). She secretly dreamed of teaching children, but gave up because it was considered improper for women to be teachers in her era. Through a strange turn of events, she time-travels to the modern era and ends up in the body of Iroha Nashiki, standing at the teacher's podium. Iroha Nashiki • Origin: Reiwa (Modern era) • Occupation: Elementary school teacher • Traits: She fulfilled her long-held dream of becoming a teacher, but struggled with the dilemmas and stress unique to modern education. After a fall, her body becomes the vessel for the soul of "Iroha" from the Edo period. She is addressed as Ms. Nashiki. (The two are the same person.)

Ikuru Ichinose • Origin: Reiwa (Modern era) • Occupation: Elementary school teacher (Iroha's colleague) • Traits: He transferred to his current school after being involved in trouble with parents at his previous post. He notices Iroha's strange behavior (the fact that her soul has changed) and, for some reason, ends up living with her in the modern world. He is addressed as Mr. Ichinose.

Takakazu Seki • Origin: Mid-Edo period • Status/Occupation: Accountant at Edo Castle / Wasan teacher at a mathematics academy • Traits: Acquired extraordinary mathematical talent through self-study. He bonded deeply with Iroha through mathematics and highly valued her talent regardless of social status. He is Iroha's "irreplaceable beloved." Iroha addresses him as Lord Seki.

Renji Sano • Origin: Reiwa (Modern era) • Occupation: A freelancer working multiple jobs • Traits: A modern man who is the spitting image of Takakazu Seki from the Edo period. He is a single father whose child attends the elementary school where Iroha works, and he works hard to make ends meet. His child is in Majima's class. He is addressed as Mr. Sano by teachers and other parents.

Rinka Saeki • Occupation: Professional poker player • Personality: A cool, solitary type who doesn't follow the crowd, but shows an innocent side to those she trusts. While aware of her childhood friend Ikuru's feelings, she maintained a "friends with benefits" relationship, but Iroha's appearance begins to change her heart. Ikuru calls her Rinka.

Saya Ichinose • Origin: Reiwa (Modern era) • Grade: 9th grade (3rd year of junior high) • Situation: Currently a truant (not attending school) • Relationship with Ikuru: Currently living in her older brother Ikuru's apartment. Ikuru calls her Saya.